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  Method for manufacturing piezoelectric ink-jet printheadUSPTO Application #: 20070019042Title: Method for manufacturing piezoelectric ink-jet printhead Abstract: A piezoelectric ink-jet printhead and a method for manufacturing the same, wherein the piezoelectric ink-jet printhead is formed by stacking three monocrystalline silicon substrates on one another and adhering them to one another. The three substrates include an upper substrate, through which an ink supply hole is formed and a pressure chamber is formed on a bottom surface thereof; an intermediate substrate, in which an ink reservoir and a damper are formed; and a lower substrate, in which a nozzle is formed. A piezoelectric actuator is monolithically formed on the upper substrate. A restrictor, which connects the ink reservoir to the pressure chamber in flow communication, may be formed on the upper substrate or intermediate substrate. (end of abstract) Agent: Lee & Morse, P.C. - Falls Church, VA, US Inventors: Jae-woo Chung, Jae-chang Lee, Seung-mo Lim USPTO Applicaton #: 20070019042 - Class: 347068000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070019042. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This is a divisional application based on pending application Ser. No. 10/321,604, filed Dec. 18, 2002, the entire contents of which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an ink-jet printhead. More particularly, the present invention relates to a piezoelectric ink-jet printhead made on a silicon substrate, and a method for manufacturing the same using a micromachining technology. [0004] 2. Description of the Related Art [0005] In general, ink-jet printheads are devices for printing a predetermined color image by ejecting small droplets of printing ink at a desired position on a recording sheet. Ink ejection mechanisms of an ink-jet printer are generally categorized into two different types: an electro-thermal transducer type (bubble-jet type), in which a heat source is employed to form bubbles in ink thereby causing an ink droplet to be ejected, and an electromechanical transducer type, in which an ink droplet is ejected by a change in ink volume due to deformation of a piezoelectric element. [0006] A typical structure of an ink-jet printhead using an electromechanical transducer is shown in FIG. 1. Referring to FIG. 1, an ink reservoir 2, a restrictor 3, an ink chamber 4, and a nozzle 5 for forming an ink passage are formed in a passage forming plate 1. A piezoelectric actuator 6 is provided on the passage forming plate 1. The ink reservoir 2 stores ink supplied from an ink container (not shown), and the restrictor 3 is a passage through which ink is supplied to the ink chamber 4 from the ink reservoir 2. The ink chamber 4 is filled with ink to be ejected. The volume of the ink chamber 4 is varied by driving the piezoelectric actuator 6, thereby a variation in pressure for ink ejection or in-flow is generated. The ink chamber 4 is also referred to as a pressure chamber. [0007] The passage forming plate 1 is formed by cutting a plurality of thin plates formed of ceramics, metals, or plastics, forming a part of the ink passage, and then stacking the plurality of thin plates. The piezoelectric actuator 6 is provided above the ink chamber 4 and includes a piezoelectric thin plate stacked on an electrode for applying a voltage to the piezoelectric thin plate. As such, a portion of the passage forming plate 1 forming an upper wall of the ink chamber 4 serves as a vibration plate 1 a to be deformed by the piezoelectric actuator 6. [0008] The operation of a conventional piezoelectric ink-jet printhead having the above structure will now be described. [0009] If the vibration plate 1ais deformed by driving the piezoelectric actuator 6, the volume of the ink chamber 4 is reduced. As a result, due to a variation in pressure in the ink chamber 4, ink in the ink chamber 4 is ejected through the nozzle 5. Subsequently, if the vibration plate 1ais restored to an original state by driving the piezoelectric actuator 6, the volume of the ink chamber 4 is increased. As a result, due to a variation in a pressure in the ink chamber 4, ink stored in the ink reservoir 2 is supplied to the ink chamber 4 through the restrictor 3. [0010] A conventional piezoelectric ink-jet printhead is shown in FIG. 2. FIG. 3 illustrates a cross-sectional view of the conventional piezoelectric ink-jet printhead in a lengthwise direction of a pressure chamber of FIG. 2. FIG. 4 illustrates a portion of a cross-sectional view taken along line A-A' of FIG. 3. [0011] Regarding to FIGS. 2 through 4, the conventional piezoelectric ink-jet printhead is formed by stacking a plurality of thin plates 11 to 16 and then adhering the plates to one another. More specifically, a first plate 11, on which a nozzle 11 a through which ink is ejected, is formed and is the bottom of the printhead. A-second plate 12, on which an ink reservoir 12aand an ink outlet 12bare formed, is stacked on the first plate 11. A third plate 13, on which an ink inlet 13aand an ink outlet 13b-are formed, is stacked on the second plate 12. An ink supply hole 17, through which ink is supplied to the ink reservoir 12afrom an ink container (not shown), is provided on the third plate 13. A fourth plate 14, on which an ink inlet 14aand an ink outlet 14bare formed, is stacked on the third plate 13. A fifth plate 15, on which a pressure chamber 15a, both ends of which are in flow communication with the ink inlet 14aand the ink outlet 14b, respectively, is formed and is stacked on the fourth plate 14. The ink inlets 13aand 14aserve as a passage through which ink is supplied to the pressure chamber 15afrom the ink reservoir 12a. The ink outlets 12b, 13b, and 14bserve as a passage through which ink is ejected to the nozzle 11 a from the pressure chamber 15a. A sixth plate 16 for closing the upper portion of the pressure chamber 15ais stacked on the fifth plate 15. A driving electrode 20 and a piezoelectric layer 21 are formed as a piezoelectric actuator on the sixth plate 16. Thus, the sixth plate 16 serves as a vibration plate operated by the piezoelectric actuator, and the volume of the pressure chamber 15aunder the sixth plate 16 is varied according to the deformation of the vibration plate. [0012] In general, the first, second, and third plates 11, 12, and 13 are formed by etching or press-working a metal thin plate, and the fourth, fifth, and sixth plates 14, 15, and 16 are formed by cutting a ceramic material having a thin plate shape. Meanwhile, the second plate 12 on which the ink reservoir 12ais formed, may be formed through injection molding or press-working a thin plastic material or an adhesive having a film shape, or through screen-printing an adhesive having a paste shape. The piezoelectric layer 21 formed on the sixth plate 16 is made by coating a ceramic material having a paste shape with a piezoelectric property and sintering the ceramic material. [0013] As described above, in order to manufacture the conventional piezoelectric ink-jet printhead shown in FIG. 2, a plurality of metal plates and ceramic plates are separately processed using various processing methods, and then are stacked and adhered to one another using a predetermined adhesive. In the conventional printhead, however, the number of plates constituting the printhead is quite large, and thus the number of processes of aligning the plates is increased, thereby increasing an alignment error. If an alignment error occurs, ink is not smoothly supplied through the ink passage, thereby lowering ink ejection performance of the printhead. In particular, as high-density printheads have been manufactured in order to improve printing resolution, improvement of precision in the above-mentioned alignment process is needed, thereby increasing manufacturing costs. [0014] However, the plurality of plates constituting the printhead are manufactured of different materials using different methods. Thus, a printhead manufacturing process becomes complicated, and it is difficult to adhere different materials to one another, thereby lowering production yield. [0015] Further, even though the plurality of plates may be precisely aligned and adhered to one another in the printhead manufacturing process, due to a difference in thermal expansion coefficients between different materials caused by a variation in ambient temperature when the printhead is used, an alignment error or deformation may still occur. SUMMARY OF THE INVENTION [0016] The present invention provides a piezoelectric ink-jet printhead, in which elements are integrated on three monocrystalline silicon substrates using a micromachining technology in order to realize a precise alignment, improve the adhering characteristics, and simplify a printhead manufacturing process, and a method for manufacturing the same. [0017] According to an aspect of the present invention, there is provided a piezoelectric ink-jet printhead. The piezoelectric ink-jet printhead includes an upper substrate through which an ink supply hole, through which ink is supplied, is formed and a pressure chamber, which is filled with ink to be ejected and having two ends, is formed on a bottom of the upper substrate, an intermediate substrate on which an ink reservoir, which is connected to the ink supply hole and in which supplied ink is stored, is formed on a top of the intermediate substrate, and a damper is formed in a position which corresponds to one end of the pressure chamber, a lower substrate in which a nozzle, through which ink is to be ejected, is formed in a position which corresponds to the damper, and a piezoelectric actuator formed monolithically on the upper substrate and which provides a driving force for ejecting ink from the pressure chamber. A restrictor, which connects the other end of the pressure chamber to the ink reservoir, is formed on at least one side of the bottom surface of the upper substrate and the top surface of the intermediate substrate, and the lower substrate, the intermediate substrate, and the upper substrate are sequentially stacked on one another and are adhered to one another, the three substrates being formed of a monocrystalline silicon substrate. The upper substrate may. have a thickness of about 100 to 200 micrometers, preferably, about 130 to 150 micrometers. The intermediate substrate may have a thickness of about 200 to 300 micrometers, and the lower substrate may have a thickness of about 100 to 200 micrometers. [0018] In an embodiment of the present invention, a portion forming an upper wall of the pressure chamber of the upper substrate serves as a vibration plate that is deformed by driving the piezoelectric actuator. Preferably, the upper substrate is formed of a silicon-on-insulator (SOI) wafer having a structure in which a first silicon substrate, an intermediate oxide layer, and a second silicon substrate are sequentially stacked on one another, the pressure chamber is formed on the first silicon substrate, and the second silicon substrate serves as the vibration plate. Preferably, in the SOI wafer, the first silicon substrate is formed of monocrystalline silicon and has a thickness of about several tens to several hundreds of micrometers, the thickness of the intermediate oxide layer is from about several hundred angstroms to 2 micrometers, and the second silicon substrate is formed of monocrystalline silicon and has a thickness of from about several micrometers to several tens of micrometers. [0019] It is also preferable that the pressure chamber is a plurality of pressure chambers arranged in two columns at both sides of the ink reservoir, and in this case, in order to divide the ink reservoir in a vertical direction, a barrier wall is formed in the reservoir in a lengthwise direction of the ink reservoir. [0020] In addition, a silicon oxide layer may be formed between the upper substrate and the piezoelectric actuator. Here, the silicon oxide layer suppresses material diffusion and thermal stress between the upper substrate and the piezoelectric actuator. [0021] It is also preferable that the piezoelectric actuator includes a lower electrode formed on the upper substrate, a piezoelectric layer formed on the lower electrode to be placed on an upper portion of the pressure chamber, and an upper electrode, which is formed on the piezoelectric layer and which applies a voltage to the piezoelectric layer. The lower electrode preferably has a two-layer structure in which a titanium (Ti) layer and a platinum (Pt) layer are stacked on each other, and the Ti layer and the Pt layer serve as a common electrode of the piezoelectric actuator and further serve as a diffusion barrier layer which prevents inter-diffusion between the upper substrate and the piezoelectric layer. Continue reading... Full patent description for Method for manufacturing piezoelectric ink-jet printhead Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method for manufacturing piezoelectric ink-jet printhead patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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